LINNEAK SOCIETY OF LONDON. 55 



upon the ground, frequently in soil rich in humus, and the rusty- 

 spored forms largely upon rotten wood, old stumps, &c. 



It would be instructive if carefid records were made of spore- 

 colonition in relation to the substratum as well as to light and 

 shade. 



Experimental Studies in the Specific Value of Morphological 

 Characters in the Fungi. By William B. Bkierley. (Com- 

 muuicated by Capt. A. W. Hill, F.L.S.) 



[Read 21st February, 1918.] 



In all systematic treatment of the Fungi there is implied 

 constancy of morphological characters, and particularly of the size 

 and shape of the mature reproductive bodies or spores. An 

 experimental study of the specificity of these criteria is in process, 

 the work being carried out primarily upon the fungus Botrytis 

 cinerea. This species is contained in the " Foh/actis^' group of the 

 genus, and the species in this group are separated partly by 

 reason of their different hosts, but more critically by minute 

 differences in the branching and septation of the conidiophore and 

 by the size and shape of the spore. 



The published spore-measurements of Botrytis cinerea show a 

 singular hick of uniformity (Marshall Wnrd on lily, 20-25 /i x 

 15 /Li; Lorriiiu Smith on gooseberry, 8-11 /x x 4-6^; K. E. 

 Smith on lime trees, up to 30 ^t; etc.), and during tlie present 

 investigation observations of the mode-spores of Botrytis cinerea 

 growing upon different hosts, or separate infections of the same 

 host, have shown that this variation in size and shape is a very 

 marked feature of the fungus (on alder twig mode-spore 3 ^ X 2 yu ; 

 on tomato fruit 10^ x 10 /x ; on onion bulb 6-5^ x 3-5^; on lily 

 14^ X lOjLt; etc.). 



Pedigree cultures derived from single spores of the fungus 

 growing upon different hosts were made, and these weie used as 

 the basis for all critical experimental work. 



Botrytis cinerea developing upon living cabbage possesses a 

 certain mode-spore. If this strain be inoculated into tomato 

 fruits, the mode-spore is different in size and shape; and a third 

 host produces a third mode-spore. The Fungus gi owing upon 

 onion bulb shows a characteristic mode-spore, and if this strain 

 be inoculated into cabbage, tomato, etc., the mode-spores differ 

 from each other and from those produced hj the th'st strain. 

 Variations and combinations of these experimental inoculations 

 w-ere carried out with strains of different origin, the substrata 

 being living plants, steamed tissues, and syntheiic media, and the 

 sizes and shapes of the mode-spores were recorded. It became 

 evident that the species Botrytis cinerea is not " uiigeheuer 

 variabel " (Liudau), but that its apparent variability is due to the 

 fact that it contains a great number of " elementary species " or 



